A brief history lesson for the youngsters:
Long, long ago, in a world before cd’s, mp3/4’s, ithings & interwebs. Music was pressed onto round black discs, with modulated spiral grooves.
“Records” or “Vinyl” (the material most commonly used after the1950’s) came in 3 common sizes 7", 10" and 12", with varying speed requirements 78rpm, 45rpm and 33rpm.
George “Porky” Peckham (an English record cutting engineer) often signed his master discs as “Porky prime cuts”.